$\dfrac{7}{2} - \dfrac{3}{8} = {?}$
Solution: $ = {\dfrac{7 \times 4}{2 \times 4}} - {\dfrac{3 \times 1}{8 \times 1}} $ $ = {\dfrac{28}{8}} - {\dfrac{3}{8}} $ $ = \dfrac{{28} - {3}}{8} $ $ = \dfrac{25}{8}$